1. Field
The present disclosure is directed to lubricating oil compositions, such as engine oils, containing acyl N-methyl glycine derivatives. For example, it is directed to lubricating oil compositions containing acyl N-methyl glycine derivatives as friction modifiers for reducing one or both of thin film friction and boundary layer friction.
2. Description of the Related Technology
Lubricating oil compositions play an important role in ensuring smooth operation of machinery, like engines. These compositions may lubricate a variety of sliding parts in an engine including, for example, piston rings/cylinder liners, bearings of crankshafts and connecting rods, valve mechanisms including cams and valve lifters, and the like. Lubricating oil compositions may also play a role in cooling the inside of an engine and dispersing combustion products. Further possible functions of lubricating oil compositions may include preventing or reducing rust and corrosion.
There are several classes of lubricating compositions including engine oils, gear oils, tractor oils, multifunctional oils, and the like. Each type of lubricating composition may require customized properties for the particular application in which it is to be used.
The principle consideration for engine oils is to prevent wear and seizure of parts in the engine. Lubricated engine parts operate mostly in a state of hydrodynamic or full fluid lubrication, but valve systems and top and bottom dead centers of pistons/cylinder liner contact zones are likely to be in a state of thin-film (elastohydrodynamic) and/or boundary lubrication. The friction between these parts in the engine may result in significant energy losses and thereby reduce fuel efficiency. Many types of friction modifiers have been used in engine oils to decrease frictional energy losses.
Improved efficiency may be achieved when friction between moving parts is reduced. Thin-film friction is the friction generated by a fluid, such as a lubricant, moving between two surfaces, when the distance between the two surfaces is very small. It is known that some additives form films of different thicknesses, which can have an effect on thin-film friction. Some additives normally present in engine oils, such as zinc dialkyl dithiophosphate (ZDDP) are known to increase thin-film friction. Though such additives may be required for other reasons such as to protect engine parts, the increase in thin-film friction caused by such additives can reduce operating efficiency.
Reducing boundary layer friction in engines may also enhance fuel efficiency. The motion of contacting surfaces in an engine may be retarded by boundary layer friction. Non-nitrogen-containing, nitrogen-containing, and molybdenum-containing friction modifiers are sometimes used to reduce boundary layer friction.
In recent years there has been a growing desire to employ lower friction lubricating oils to provide higher energy efficiency, such as providing lower friction engine oils to improve fuel efficiency. The present disclosure provides an improved lubricating oil composition that may reduce one or both of thin film friction and boundary layer friction. The present disclosure is directed to lubricating oil compositions containing acyl N-methyl glycine derivatives as friction modifiers for reducing one or both of thin film friction and boundary layer friction.
U.S. Pat. No. 5,599,779 discloses a rust inhibitor composition consisting of a three component rust inhibitor package including a compound of the formula:
wherein R represents a C8-18-alkyl or alkenyl group;
a dicarboxylic acid of the formula:
wherein x is an integer from 4 to 46; and
an amine of the formula:
wherein R1, R2, and R3 are independently selected from hydrogen, hydrocarbyl having up to 14 carbon atoms, hydroxyalkyl, cycloalkyl or polyalkyleneoxy groups. The rust inhibitor package is described as advantageous for use in a grease, and may be formulated with oils and waxes into rust preventative compositions for use in automotive and other industries.
WO 2009/140108 discloses the use of variety of different rust inhibiting compounds for certain types of multifunctional oils. In the specification there is a brief mention of the possibility of using a compound of the formula:

wherein R and R1 are not defined. No further details are given as to the amounts that should be used, nor are any specific formulations including such compounds exemplified in the application.
GB 1235896 discloses multifunctional lubricants and includes an example of a wet brake formulation including oleoyl sarcosine. The exemplified composition also includes basic calcium sulphonate detergent (TBN=300), P2S5—polybutene barium phenate/sulphonate detergent, a dispersant that is a reaction product of polybutenyl succinic anhydride with an Mw=900 PIB group and tetraethylene pentamine, zinc dihexyl dithiophosphate, dioleoyl phosphite, sperm oil, and sulphurised polybutene.